Silicon wafer sizes used in the semiconductor industry are nowadays 100 mm in diameter minimum. The conversion of the present semiconductor industry from 200 mm to 300 mm diameter silicon wafers is a new challenge for chip manufacturers. The main motivation for the conversion to larger wafer sizes is the fact that more chips may be produced using the same effort in skilled manpower and resources. A possible reduction in cost per function (by technology improvements or by reduction of manufacturing costs) is a basic driving force for the microelectronics industry. Currently, reduction of costs can be obtained by increased equipment productivity, reduction in start-up time of fabs, reduction in queue time and using cost of ownership principles. Increasing the wafer size, may well have a negative impact on these possible cost reductions. When changing the wafer size, most effort and money will be spent on making sure the wafer is processed uniformly, to keep the throughput of chips high. Less money is available for secondary equipment and manufacturing improvements. However, lithographic steps are the most expensive steps in IC manufacturing. The throughput of this step determines the overall throughput of the IC manufacturing line and manufacturing cost.
U.S. Pat. No. 4,810,616 describes a work holder for holding a plurality of ceramic pieces. Each ceramic piece may be used for holding one integrated circuit. The holder is designed so that conductive wiring may be applied to the ceramic pieces. Each ceramic piece is held in place by a metallic spring. The work holder may also be made of metal. This type of work holder and piece fixing method cannot be used in the processing of integrated circuits and is remote from the present invention. The known holder would generate considerable amounts of contamination in the finished IC's through contact diffusion from the metal spring and/or work holder into the active devices of the IC when carrying out a thermal treatment step at 450.degree. C. or above, e.g. during CVD deposition of dielectrics, annealing after implant of doping, epitaxy deposition of layers, silicidation, oxidation, nitridation. At least one of these processes is essential in the manufacture of an IC. Information about contamination and how to prevent it may be obtained from "Ultra-clean surface processing of silicon wafers," by Takeshi Hattori, Springer Verlag, 1998.
The object of the invention is to present a new basic concept for chip manufacturing which provides an answer to the current economic challenges for chip manufacturers.
It is a further object of the present invention to provide a method and apparatus for manufacturing integrated circuits which are more economic and more easily optimized.